Lining for casting mold cavities



March 14, 1933. J. D. ALLEY LINING FOR CASTING MOLD CAVITIES original Filed A ug. 22, 1929 Patented Mu. i4, 1933 UNITED STATES PATENT OFFICE JOHN I). ALLEY, OF PITTSBURGH, PENNS YLVANIA.,y ASSIGNOB T THE AMERICAN TION OF DELAWARE LINING FOIE. CASTING MOLD OAV'ITIES original appIication led August v22, 1929, Serial No.

387,817. Divided and this application led June 1,

1932. Serial No. v614,697'.

a division of my origf This application yis filed Auinal application-Serial No. 387,817, gust 22, 1929. l

The invention relates to casting molds and its object is primarily to provide all or a portion of the Wall of the mold cavity with a lining of low thermalconductivity to prevent chilling the casting, capable of resisting repeated heatl shocks without cracking, spalling, or breaking down, and strong and substantial to withstand the wear and tear of repeated casting operations.

I have found that a composition composed largely of fused silica and with a suitable bonding material answers all of these requirements. The essential properties of fused vsilica which make it desirable are it is a vitreous material Without crystalline structure, it has low thermal conductivity, and it has-a low 'coefficient of expansion. Bonding; clays are used which will vitrify at less temperature than that required to devitrifyfused silica.

My invention may be embodied in a lining of any dimensions and configuration for a mold for making any kind of casting. I have used the invention in an iron mold for i i making brake shoes in which the Wall of the mold cavity was partly or entirely lined with blocks or sections made in accordance with my invention and for this reason I will show and describel the invention as embodied in brake shoe molds. I

In the accompanying drawing illustrating the invention in a selected type of Ibrake shoe mold, l

Fig. 1 is a longitudinal sectional view of the mold in which the wall of the mold cavity is principally but not entirely provided with a refractory lining.

Fig. *2 is a transverse' sectional view on the' line 2-2 of Fig. 1.

Fig. 3 is a longitudinal sectional view-simblar to Fig. 1 showing the mold cavity wall fully lined with refractory material.

Referring to the drawing, 4 is the cope and 5 is the drag of the mold, the cope being cen- I tered and seated on the drag in any suitable manner and provision being made for removing the cope from the drag at the conclusion enough relatively coarse aggregate to make a 100 fractory binder.

of the casting operation by any suitable means. A pouring gate 6 is providedat any desired location in the mold through which the molten metal is poured into the mold cavity 7 formed partlyv in the colpe and partly in the drag. The type of bra e shoe to be produced in the mold of Figs. 1 and 2 is a cast iron shoe having its end portions chilled and other parts unchilled. Forthisfpurpose the cope has a lining block 8 and the drag has a lining block 9 seated therein to form the wall of the mold cavity except at theend portions 10 which'are formed by the metal of the cope and drag. A reenforceback 11 with the lug strap 12 and lug core 1-3are held in place at the top of the mold cavity by a wire 14 passing through .the vent openings 415 or in this mold will be un'chilled except at the ends which will be chilled where the Imolten metal contacts with the iron of the mold. The moldv of Fig'. 3 is the same as the mold ofv Figs. 1 and 2 except thatI the lining sections 8', 9 alsdform the ends of the mold cavity.-

A typical composition which I have found satisfactory for lining a brake shoe mold cavity consists of 60% fused silica and 40% re- The refractory binder may consist of 50% Kentucky ball'clay and 50% GeorgiaV ka-olin. The percentage of clays may vary from 15% to 50% with a corresponding change in the proportion of fused silica. I may also use a percentage of silicon carbide for a part of the fused silica, in a 'composition as follows: 40% fused silica,

% silicon carbide, 20% Kentucky ball'clay, and 20% Georgia kaolin. The thermal conductivity of silicon carbide is comparatively vhigh and it is not desirable to use more than of it in .substitution for fused silica.

In preparing the composition I proceed as follows: all materials should be `ground or crushed to pass through a relatively ine screen, dependihg upon the quality of the refractory desired. Of each material I have used approximately one-half of 20 to 80 mesh and one-half of 80 mesh and liner to provide a compact aggregate and a dense refractory with smooth face, without voids, and with in any other suitable manner. The shoe cast structurally strong body. The material should be thoroughly mixed in a dry-pan, in a pug mill, or in any other suitable manner. The blocks or sections or liners for lining in Whole or in part the walls of the mold cavity may be formed from a wet mix by molding or by pressing; or they may be formed from what is commonly known as a dry mix, which contains about 7% of water, under pressure of as much as one ton or more per square inch. After the refractory shapes are formed they are thoroughly dried to drive off excess moisture and then they are heated. This heat treatment should be suliicient to vitrify the binder without devitrifying the fused silica and the temperature shoud be maintained until all the binder is vitriied, and followed by slow cooling depending upon the size and section of the shapes. For example, the heat treatment may be continued in a suitable furnace for a period of about four to five hours up to 2100 F. and then for about six hours at 52100o F. followed by about twelve to fifteen hours slow cooling in the furnace. It is portant that the firing temperature should not be carried to a degree which would tend to devitrify the fused silica and change it into a crystalline form sensitive to heat shocks.

The shapes or blocks are made as required to form in Whole or in part the Walls of the mold cavity in an iron mold otherwise often referred to as a permanent mold or as a repetition mold. The lining prevents the cast metal from chilling, it does not crack or spall or break down under the repeated heat shocks of repetition casting operations, and it is structurally strong and substantial 'to withstand the Wear and tear of repeated casting operations.

I have given herein examples of materials and proportions and have also given firing periods and temperatures which have been found to be satisfactory in producing lining shapes for use in iron molds for casting brake shoes, but I do not thereby limit the invention to these particular specifications because it will be apparent to those skilled in the art that they ma be varied more or less to suit different con itions and to make linings for different molds. I have also given certain clay materials which I consider most desirable for the purpose but other materials producing the same or equivalent results may be substituted.

I claim:

1. A lining of low thermal conductivity and capabeof resisting repeated heat shocks for a casting mold cavity lining and consisting of fused silica and a refractory binder composed of Kentucky ball clay and Georgia kaolin.

2. A lining for a casting mold cavity consisting of fused silica and a refractory binder consisting of Kentucky ball clay and Georgia kaolin, the. fused silica being in excess of the refractory binder.

3. A lining for a casting mold cavity consisting of substantially fused silica and 40% refractory binder, said refractory binder consisting of substantially 50% Kentucky ball clay and 50% Georgia kaolin.

JOHN D. ALLEY. 

